Audiometer with tone control



Feb. 17,

Filed Feb. 9, 1966 L'. H. ECKSTEIN ET-AL AUDIOMETER WITH TONE CONT-no1.

2 Sheets-Sheet 1 van/var L. H. ECKs'rElN E'rAl. 3,496,296 AUDI'OKHETER- WITH TONE CONTROL 2 Sheets-Sheet 2 Feb.1 7,197o

Filed Feb. 9. 1966 i United States Patent O 3,496,296 AUDIOMETER WITH TONE CONTROL Leo H. Eckstein, 11350 Kingsland St. 90066, and Joel Eckstein, 8563 Colgate St. 90048, both of Los Angeles,

Calif.

Filed Feb. 9, 1966, Ser. N0. 526,138

Int. Cl. Glk 10/00 U.S. Cl. 179--1 3 Claims ABSTRACT F THE DISCLOSURE The present invention is concerned with alternating current electronic switching circuitry, such as diagnostic audiometer systems, and related instruments; and the invention is particularly concerned with an improved audiometer system for determining whether a patient has certain types of hearing defects, this being achieved by testing the response of one ear of the patient relative to the other.

The switching circuit of the invention finds particular utility in conjunction with diagnostic audiometer systems and, for that reason, will be described in such an environment. It will become evident as the description proceeds, however, that the switching circuitry of the invention has general utility.

Audiometry is the quantitative assessment of the hearing of an individual, either normal or defective. The audiometer is widely used for this purpose. The usual audiometer includes an oscillator, an amplifier, and an appropriate attenuator for controlling the intensity of the audio signals generated by the instrument.

The audiometer may be used for the diagnosis and treatment of hearing defects which are manifested by the person hearing in one ear differently than in the other ear. Specifically, for hearing defects such that when a particular tone is transmitted to a person, one ear hears the tone in its actual pitch, but the other ear hears the tone at a different pitch.

For example, if such a patient is provided with earphones, and a tone of a particular frequency in the audio range is introduced to both earphones, he will be under the impression that the tone heard by one ear is different from the tone heard by the other. This type of hearing defect is referred to as diplacusis.

Moreover, should a patient suffering from displacusis be asked to adjust one or both of the tones, so that it appears to him that both ears are hearing the same tone, he will ordinarily make adjustments such that the tone applied to one ear is actually at a higher or lower frequency than the tone applied to the other ear. Calibrated dials will indicate the extent of the aberration.

Other types of hearing defects including, for example, a relative degree of deafness between the two ears of the patient. Then, although the tone applied to both ears appear to such a patient to have the same ptich, one tone appears to be at a lower intensity than the other. This latter hearing defect may be tested quantitatively, by asking the patient to adjust the intensity of the tone applied to one ear, for example, until both tones appear to have the same volume. As in the preceding case, suitable calibra- 3,496,296 Patented Feb. 17, 1970 ICC tions can be provided so that the extent of the hearing defect may be quantitatively measured.

The ordinary prior art equipment for measuring relative defects between the ears of a patient usually involves two audiometers, or one audiometer equipped with two channels each with its own oscillator. In the case of the equipment for diagnosing and measuring diplacusis, one of the audiometers of such a prior art system would present a tone in the audio frequency range, for example, in the range of 12S-8000 cycles, and this tone would be applied to one ear. The other audiometer would also provide a tone in the audio frequency range, which would be applied to the other ear.

Both audiometers in the prior art system would then be adjusted so that tones of the same frequency are applied to both ears of the patient. The patient would then be asked to adjust the frequency of one of the audiometers, so as to vary the pitch of the tone until, to his preception, both tones appear to have the same pitch. This adjustment would be on a calibrated scale, and Would usually extend through a range of, for example, i10%.

In the latter prior art case whereby relative deafness of the two ears is measured, attenuators are provided in each of the channels which extend from the separate audiometers to the respective earphones for the left and right ears of the patient. The patient then adjusts attenuators in the two channels, until both tones appear to have the same intensity. Again, calibrated dials indicate the extent of the adjustment, so that the hearing defeat of the patient can be determined quantitatively.

In either case, therefore, the patient controls the tones applied to his left and right ears, until the first tone matches the second tone, insofar as his hearing is concerned. Then, the calibrated dials indicate the extent of his particular hearing defect.

The improved instrument of the present invention, unlike the prior art devices, utilizes but a single oscillator or audiometer. The equipment of the invention functions in a manner, as will be explained in detail, such that gate circuits are selectively activated to pass the selected audio signal from the audiometer, first to one ear and then to the other.

In the case of the diplacusis test, in the use of the system of the invention, a frequency controlling circuit is provided, so that whenever the audiometer is switched to one of the ears, its frequency is simultaneously varied from a selected frequency to a second, adjustable frequency.

In the case of the relative deafness test, in the use of the system of the invention, separate attenuators may be provided in each of the channels, so that as the audiometer is switched from one channel to the other, the patient makes necessary adjustments, so as to bring the two tones up to the same amplitude level, insofar as his perceptions are concerned.

The use of a single audiometer, especially in the case of the diplacusis diagnosis, is most advantageous in permitting accurate diagnosis to be made. This is because, when two present day audiometers are used, for example, they may actually differ by as much as ten percent in actual frequency, and yet fall Within accepted calibration standards. Therefore, with the prior art systems, it is difficult to determine whether or not the patient actually has diplacusis, or whether instrument error is involved. In the system of the present invention, and since a single audiometer oscillator is used, there is no such possibility of instrument error.

In addition, the system of the present invention provides for the tone from the audiometer to be alternately pulsed between the two ears. This is in contradistinction to the prior art concept of providing a continuous tone in each ear. It has been found in practice that the patient physiologically is more perceptive to pulsed alternate tones than to continuous tones in both ears; and the patient can make more precise adjustments in matching the tones in accordance with his hearing capabilities.

A further advantage of the system and instrument of the present invention, as compared with the prior art devices, is that any known type of audiometer can be used for the required diagnosis, without modilication, and merely by interposing an accessory instrument, incorporating the gate and control circuitry of the invention, between the audiometer and the earphones.

An object of the present invention, therefore, is to provide an improved system for diagnosing and measuring particular types of hearing defects, which system is eminently simple in its construction and which requires but one audio signal source for testing the relative responses of the two ears of the patient.

Other objects and advantages of the invention will become more apparent from a consideration of the following description, when the description is taken in conjunction with the accompanying drawings, in which:

FIGURE l is a block diagram of one embodiment of the invention;

FIGURE 2 is a block diagram of a second embodiment; and

FIGURE 3 is a circuit diagram of the embodiment of FIGURE 1.

The system of FIGURE 1 includes an audio oscillatoramplifier unit 10. This unit, for example, may be in the form of a commercially available audiometer. These audiometers, as is well known, are usually adjustable throughout the audio range, so that tones of any selected pitch can be derived therefrom.

The output from the amplifier portion of the audiometer is applied to a pair of gates 12 and 14. These gates, and the other components of the system, may be of the solid state type, and may be constructed as wellknown transistor circuits.

A switching unit 16, which may, for example, be a multivibrator of the free-running type, may be connected to the gates 12 and 14. The connections between the freerunning multivibrator 16 and the gates 12 and 14 are such that, when the multivibrator is in its rst state, the gate 12 is conditioned to pass the tone from the audiometer 10 to its output; and when the multivibrator 16 is in its second state, the gate 14 is conditioned to pass the tone from the audiometer to its output.

The gate 12 is connected to an adjustable attenuator 18 which, in turn, is connected to an earphone 20. The gate 14, on the other hand, is coupled to an adjustable attenuator 22. The latter attenuator is connected to a second earphone 24. The earphone 20 is intended to be worn on one ear of the patient being diagnosed or treated, and the earphone 24 is intended to be worn on the other ear.

In using the apparatus and system of FIGURE 1, the audiometer 10 is adjusted so that it generates a tone of a selected frequency Within the audio range. This tone is passed alternately by the gates 12 and 14 to the attenuators 18 and 22 and through the attenuators to the respective earphones 20 and 24.

The attenuators are adjusted by the patient until the tones applied to both ears appear to him to be at the same amplitude level. The adjustments of the attenuators are calibrated, so that any actual difference in the intensity of the two tones may be indicated, so that the degree of deafness in one ear with respect to the other can be measured quantitatively.

The system of FIGURE 2 is similar in some respects to the system of FIGURE 1, and like components have been designated by the same numbers. However, the latter system is intended to introduce tones of adjustably different frequencies to the two ears of the patient, so

4 that it may be determined as to whether or not he is suffering from the disease known as diplacusis.

As before, the tone from the audiometer 10 is applied to the gates 12 and 14. These gates may be connected directly to the earphones 20 and 24. Also, the free-running multivibrator controls the two gates 12 and 14 as in the previous embodiment. It might be stated at this point that the free-running multivibrator 16 may have any appropriate circuitry and, since such multivibrators are extremely well known at present, it is believed that a detailed circuit diagram of the multivibrator is unnecessary for the complete understanding of the system of the present invention. This also applies to the actual circuitry involved in the audio oscillator and amplifier components which make up the audiometer 10.

The system of FIGURE 2 includes an additional component which is designated as an oscillator gate 30. However, this gate may be a relay, or any other appropriate switching circuit. The gate 30 responds to the output of the multivibrator 16, so that it closes a circuit, whenever the multivibrator conditions the gate 14 for conduction.

The gate 30 is used to complete a circuit for a frequency controlling network 32. The frequency controlling network may include a variable capacitor, and it is connected into the tank circuit of the audio oscillator portion of the audiometer 10. The network 32 is adjustable by the patient, so that the frequency of the tone generated by the audiometer may be controlled by him.

The system operates so that when the audiometer is first adjusted to generate a selected tone, that tone is passed by the gate 12 to the earphone 20, whenever the multivibrator 16 is in its iirst state. However, when the multivibrator 16 changes to its second state, the gate 14 is not only conditioned to pass the output from the arnplier 10 to the earphone 24, but at the same time the gate 30 activates the frequency controlling circuit 32, so that the frequency of the tone passed to the earphone 24 is different from that of the tone passed to the earphone 20.

The latter frequency is under the control of the patient. That is, the patient adjusts the variable capacitor of the network 32 until both tones appear to him to be the same. Suitable calibrations may then be used to determine whether or not the tones are in fact the same, and any discrepancy provides a quantitative measurement of the extent to which the patient may Ibe suffering from diplacusis.

Although all the components of the systems of FIG- URES 1 and 2 are, in themselves, extremely well known to the art, so that, as mentioned above, a detailed explanation is deemed to be unnecessary. However, the circuit diagram of FIGURE 3 does show a portion of the system of FIGURE 1 in circuit detail so as to clarify the description. It will be appreciated that the circuits shown in FIGURE 3 can also be used for the equivalent circuits in the system of FIGURE 2.

As shown in FIGURE 3, the audiometer 10= includes an output transformer 50. One terminal of the secondary of the output transformer 50 is connected to alternatingcurrent ground, and the other terminal is connected through a coupling capacitor 52 to the collector of a PNP transistor 54 and to the collector of a PNP transistor 56. These collectors are also connected through a resistor 57 to the negative terminal of a direct-current source, the positive terminal of which is connected to a direct-current ground point. The resistor 57 may have a resistance of ohms, for example.

The capacitor 52 may, for example, have a capacity of 250 microfarads, and it constitutes a coupling capacitor, and it also serves to isolate the seconadry of the transformer 50 from the direct-current source.

The transistors 54 and 56 may be of the type presently designated 2N404. The transistor 54 is connected so as to form the gate 12, and the transistor 56 is connected to form the gate 14. The emitter of the transistor 54 is connected to the input terminal of the attenuator network 18; whereas the emitter of the transistor 56 is connected to the input terminal of the attenuator 22.

The attenuator 18 is formed, for example, of a series of shunt resistors 58, 60, 62 and 64. The resistors 60, 62 and 64 each has a resistance of 10 ohms, for example, Whereas the resistor 58 has a resistance of 20 ohms. The shunt resistors are connected to an altemating-current ground. The alternating-current ground is connected through a resistor 65 to the direct-current ground. The resistor 65 may have a resistance of 100 ohms, for example. The ungrounded terminals of the shunt resistors are interconnected by pairs of resistors 66, 68, 70, 72, 74 and 76. The resistors 60, 70 and 74 may each have a resistance of 9.1 ohms, for example, whereas the resistors 68, 72 and 76 may each have a resistance of 6.8 ohms.

It will be appreciated that the attenuator 18 may be extended by the provision of further shunt and series resistors connected to its left-hand end. The earphone 20 has one terminal connected to the altemating-current ground point, and the other terminal is connected to a movable contact arm 70 of the attenuator 18. The contact arm 78 may be moved from contact to contact along the attenuator 18, the latter contacts being connected to the junction points of the series, resistors, as shown.

The attenuator 22 may be similarly connected, and it may have a movable contact arm 80 which is manually adjustable from one of its fixed contacts to the other. The arm 80 is connected to the earphone 24 which, also, is connected to the alternating-current ground point.

As mentionel above, the gates 12 and 14 are under the control of the free-running multivibrator 16. When the multivibrator 16 is in one state, the transistor 54 is rendered conductive, so that the audio tone from the audiometer is passed to the earphone 20. Likewise, when the free-running multivibrator 16 is in its second state, the transistor 56 is rendered conductive, so that the tone is passed to the earphone 24.

The attenuators 18 and 22, in either instance, can be adjusted so that as much of the tone as desired can be attenuated. As mentioned previously, the adjustment is usually made by the patient, until, to his perception, both tones appear to be at the same amplitude level.

The free-running multivibrator, as mentioned above, can be of any known circuit configuration. In the illustrated embodiment, for example, a pair of PNP transistors 82 and 84 are included in the circuit. These transistors may also be of the type designated 2N404. Each of these transistors has its emitter grounded. The collector of the transistor 82 is coupled through a capacitor 86 to the base of the transistor 84.

The capacitor 86 may have a capacity, for example, of l microfarad. The base of the transistor 82 is connected to the negative terminal of the l8-volt source through a 470 kilo-ohm resistor 88; the collector of the transistor 82 is connected to that terminal through a 4.7 kilo-ohm resistor 90; the base of the transistor 84 is connected to that terminal through a 470 kilo-ohm resistor 92; and the collector of the transistor 84 is connected to that terminal through a 4.7 kilo-ohm resistor 94. The collector of the transistor 84 is coupled back to the base of the transistor 82 through a l micro-farad capacitor 96.

As is well known, the circuit of the free-running multivibrator 16 is a usual relaxation oscillator type. The circuit is cylindricallly triggered from a state in which the transistor 82 is non-conductive, and the transistor 84 is fully conductive, to a state in which the opposite condition applies, and vice versa. Also, this triggering will occur automatically, and at periods determined by the values of the circuit constants. This means that a first rectangular wave appears at the output terminal 98 of the multivibrator, and a second rectangular wave appears at the output terminal 100, these rectangular waves being 180 out of phase.

The output terminal 98 of the free-running multivibrator 16 is connected through a resistor 102 to the base of the transistor 54, the base being connected to a grounded capacitor 104. The resistor 102 may have a resistance of lO kilo-ohms, and the capacitor 104 may have a capacity of 5 micro-farads. Likewise, the output terminal is connected through a resistor 106 to the base of the transistor 56, the base being connected to a grounded capacitor 108. The resistor 106 and capacitor 108 may have the same respective values as the resistor 102 and capacitor 104.

The resistors 102, 106 and their corresponding capacitors 104, 108 form respective resistance-capacitance networks, and these networks serve as a protective means for protecting the transistors from large amplitude transient spikes.

In the system of FIGURE 3, the alternating-current ground point has been separated from the direct-current ground point, so as to eliminate leakage and crosscoupling; and also to provide greater flexibility in the design of the circuit.

It will be appreciated that, for the embodiment of FIGURE 2, the output terminal 100 of the free-running multivibrator 16, may also be connected to a gate similar to the gate circuits 12 and 14, and which serves to connect a variable capacitor into the frequency determining circuit of the oscillator in the audiometer 10, as described above.

It will also be appreciated that the system of the present invention, in all its embodiments, uses exactly the same audiometer oscillator to generate the tones for the two ears. This, as mentioned above, not only simplifies construction problems, in that it is necessary to have two oscillators tuned and calibrated to exactly the same point, but also serves to provide a much more precise and accurate system.

As also mentioned, the system of the invention applies the tones intermittently and alternately to the two earphones 20 and 24; rather than on a continuous basis, as is the case with all prior art systems of the same general type, with which the applicants are aware. This, as noted, has found to result in a physiological advantage, in that patients have found it easier to provide more accurate readings with alternate tones, than in the case of steady continuous tones.

It will be appreciated that while particular embodiments of the invention have been shown and described, modifications may be made. The following claims are intended to cover the modifications which fall within the spirit and scope of the invention.

What is claimed is:

1. A diagnostic audiometer system, and the like, comprlsing:

an adjustable oscillator capable of generating alternating current tone signals in the audible frequency range;

an amplifier coupled to the oscillator for amplifying the signals generated thereby and for producing amplified alternating current tone signals in said audible frequency range;

a first output circuit;

a first transistor circuit coupled to said amplifier for introducing the alternating current tone signals produced thereby to said first output circuit;

a second output circuit;

a second transistor circuit coupled to said amplifier for introducing the alternating current tone signals produced thereby to said second output circuit;

a multivibrator circuit having a first state and a second state and coupled to said first and second transistor circuits for sequentially conditioning said first and second transistor circuits alternately to pass said alternating current tone signals from said amplifier to said first and second output circuits;

adjustable circuitry comprising a manually adjustable frequency controlling circuit coupled to said oscillator to shift the frequency of the alternating current tone signals derived therefrom; and activating means for said frequency controlling circuit coupled to said multivibrator circuit to activate -said frequency controlling circuit each time said multivibrator circuit is in one of said first and second states, said adjustable circuitry serving to adjust the frequency of the audio signals passed by said second transistor circuit to said second output circuit. 2. The combination dened in claim 1 in which said multivibrator circuit includes a free running multivibrator. 3. The combination defined in claim 2 in which said rst output circuit comprises a first earphone to be worn UNITED STATES PATENTS 3,221,100 1l/l965 Towne. 2,869,666 1/1959' Webster. 3,101,390 8/1963 Maille. 3,365,544 1/ 1968 Cornett.

WILLIAM C. COOPER, Primary Examiner CHARLES JIRAUCH, Assistant Examiner 

